The present invention relates generally to mining technology and machinery in which metals are recovered from ore bearing sands. More particularly, the present invention relates to a mineral extraction machine adapted to recover fine gold particles from raw ore slurries preclassified by size.
In the prior art is it well known to provide some form of separation apparatus wherein materials of specific gravities are separated from one another through the use of conveyers, water or the like. The use of water for slurry processing is well known in the mineral extraction and processing arts. Water is often used as the medium for providing a slurry, which can thereafter be processed though filters, settling equipment, or the like. A wide variety of filters are known in the art for separating particles of different sizes from a slurry. Foraminous conveyers or drums are employed as filters for use in the de-rocking process where incoming fines are first processed. One known de-rocking apparatus of which I am familiar is the trommel. It employs a rotating, foraminous drum which constrains unwanted aggregates while passing fines of a desired size range.
Very fine deposits of gold are accumulated within the banks of certain northern rivers, such as the Liard river in the Yukon Territory, Canada. Particles of gold are carried through river water and deposited into sand banks along the river's edge, intermingled with fine river sands, silt, aggregates, and numerous particles of other unwanted contaminants. Typically the fines to be processed are a combination of silicon sand, gravel, and rocks to about twenty inches in diameter. Mixed with this are deposits of magnetite and particles of gold, silver, and platinum ranging in size from 30 to approximately 250 microns. Economically worthwhile processing has up until now been difficult. As will be appreciated by those experienced in the art of gold-fines processing, the task of obtaining a satisfactory yield of gold aggregate from a river deposit may be an extremely difficult and expensive one.
Conventional machines for fine separation which have been employed for the purposes of concentrating fine gold deposits include trombles, or rotary drum-type de-rockers, Rackard spirals which employ gravity and centrifugal force to separate heavier particles from a fine slurry, and shaker tables, such as the Gemni-brand table. Various forms of inclined sluices have been employed in the mineral recovery arts, in conjunction with one or more inputs and outputs of water. Water is often used as a separating medium because it inherently enables minerals of different specific gravities to be separated. In addition, it is known to convey and process mineral ores in a water solution. However, none of these systems taken alone have the ability to process a large enough volume of raw material to make ground paying less than ten dollars of gold per yard commercially feasible. Making a profit with aggregate paying as little as two dollars per yard is especially important in the gold fields of the far north where the mining season is only three or four months per year. Unto the present day when known systems are employed conventionally in various combinations, commercially worthwhile fine gold recovery has not been very successful.
A wide variety of systems used for different types of gold mining operations are known in the prior art. For example, U.S. Pat. No. 2,491,912, issued to M. Walker on Dec. 20, 1949 disclosures an inclined, sluice-like separating apparatus wherein a pair of spaced-apart, inclined troughs in which rotatable conveyers are disposed circulate and move materials to be separated. A drainage screen having a plurality of graduated slots enables materials to be separated through registry in the appropriate slots.
The gravel washer of U.S. Pat. No. 3,682,299 issued to Conley, Aug. 8, 1972, includes an upwardly inclined, foraminous conveyer belt which moves gravel between a lower position within water and an upper position at a discharge end. The invention seeks to remove trash from gravel without sluicing. U.S. Pat. No. 4,298,232 issued Nov. 3, 1981, provides apparatus for continuous mining wherein conveyers are employed in conjunction with the mining of coal.
U.S. Pat. No. 2,698,087 issued Dec. 28, 1954 to Call, discloses a flotation and separation tank which separates potatoes from the stones and detritus which are generally recovered during harvesting by conventional digging machines. Flow streams of water are employed within a hopper in conjunction with the rotation of foraminous belts. Water currents separate the potatoes from the unwanted materials, and both the potatoes and the contaminants are removed from the hopper by conveyers.
With respect to all known prior art, I am unaware of any machine which can properly filter gold particles or accumulations from river bank sands. I am unaware of any prior art system which can appropriately and economically filter the fines recovered from such river bank to concentrate and recover usable gold deposits.